A programmer often examines and tests an application during development in many different manners. The programmer may run the application in various use scenarios, apply loading, execute test suites, or perform other operations on the application in order to understand how the application performs and to verify that the application operates as designed.
As the programmer identifies a problem area, the programmer may locate the problem area in source code and improve or change the code in that area. Such improvements may then be tested again to verify that the problem area was corrected.